WW MK8 or WWBMG main body for 50T main gear and MK8 drive gear setup

This is dumb. 95A TPU at 41mm3/s and I bet it could do even more, but for me its enough lol. Look it at WristWatch extruder with MK8 + smooth idler pushing 95A TPU at 41mm3/s at 250C #3dprinting

It is compatible with IDGA gearsets but beware of the increased tolerances due to small difference in the filament gear diameters.

ATTENTION - IF THE BEARING FOR THE SHAFT GETS MISALIGNED/SHIFTED AWAY FROM THE FILAMENT PATH, IT WILL CAUSE EXTRUSION ISSUES. MAKE SURE THE BEARING IS CENTERED WHEN INSTALLING AND CHECK IT WHEN DOING MAINTENANCE TO THE PRINTER!

Photo above: left is misaligned bearing, right side is centered and proper. When printing in hotter chamber and having lots of force on the idler, the skinny bearing can be pushed into the plastic depending of the temperature, pressure and the plastic itself. Examples in the photo are PA6GF25 on the left and PC-ABS on the right.


Assembly goes just like with any BMG gearset and any WristWatch extruder, just the main body is different from the IDGA/RIDGA version and you can reuse IDGA smooth bearing idler as a whole. When installing the gear to the main body, leave the drive gear loose and after pushing filament through it, wiggle the gear on a proper spot on the shaft and only then tighten it.

Use threadlocker where needed. Be wary that it's far for perfectly centered like Bondtech or FYSETC billet gears, however it comes in wayyyy cheaper compared to both offerings (16+€ and they include idler gear aswell, just the main gear with shaft cannot be purchased separately, only comes as a set).

50T MK8 Specific BOM:

• 50T reduction gear for Sherpa/WW/CW/Hex with 5x28mm shaft (about 5.5€)

• MK8 drive gear for 1.75mm filament (2.7€ single or about 3€/5pc (about 0.60€/pc) if you can find like that)

• 2x MR85 smooth bearing without and edges etc (4.7€/10pc or about 0.50€ per piece) and a flathead M3x16 bolt and one tiny radius M3 washer

Main hardware (same as for A4T WW BMG/RIDGA/IDGA)
2 M3 thin square nuts
2 M3x20
1 M3x12
1 M3x16
1 M3x25
1 M3 thin washer
1 extruder spring

For smooth idler
1 685-2RS bearing
1 flathead M3x16
1 M3 thin washer

To properly install the bearing inside the main body
M5x20 or longer bolt
M5 washer
M5 nut

The slits in the front face are for easier removal of the bearings should there be need for it without damaing the printed part.

Prices for the main drive gear parts with shipping are about 7€ making it less than half what others cost. Now why shouldn't you get the BMG clones instead for a bit extra and be done with it? Well, those are actually larger in diameter when measured the filament drive radiuses and also eccentric which means even more deviation in filament drive radius. Look at the second picture where I have BMG next to MK8, both are meant for 1.75mm filament. Billet versions are at least 14€ or twice the price, but usually closer to 20€.

When measured, my OEM Bondtech RIDGA from WW extruder I replaced was 7.5mm from the tips of the filament teeth while MK8 is at 7mm in diameter. HOWEVER the teeth on MK8 drive gear are visibly deeper. While the original RIDGA is "rotation_distance: 4.45" it now should be set to "rotation_distance: 4.05". That equals do about 10% more torque compared to BMG/OEM Bondtech gearset.

Considering that the rotation_distance got reduced by almost 10%, then the torque actually got increased by a significant amount. Proof for it is in the last picture where I used ASA at 290C through Goliath hotend with TC 0.5mm nozzle without CHT geometry and if the meltzone got saturated, the 1.75mm filament that went in came out at 1.6mm through 0.5mm nozzle. Idler tension has to be a bit higher compared to some other extruders. Let the teeth dig in. For the torque look at the last photo where it pushed so much filament that it did not fully melt, rather was still in glass transition so it "rebuilt" itself after extruder from the nozzle.

minilogique/WristWatch-MK8: WristWatch extruder with a twist